Effects of drinking water with high iodine concentration on the intelligence of children in Tianjin, China.
OBJECTIVE
This study aimed to investigate the effects of drinking water with high concentrations of iodine on the intelligence of children in Tianjin, China.


METHODS
It was a population-based health survey utilizing a random cluster sampling design conducted in June 2005. Participants were recruited from the total population of primary school children attending years 1-4 with ages ranging from 8 to 10 years. Intelligence quotient (IQ) was assessed using the combined Raven's test, second edition. Linear regression analyses were applied to test for any association between water iodine concentration and IQ.


RESULTS
A total of 1229 students were recruited with a mean IQ of 105.8 (95% CI: 104.2-107.3). Water analyses indicated iodine concentrations were high in one rural region and exceedingly high in another with median values of 137.5 and 234.7 microg/l, respectively. There was a significant association between residing in the very high water iodine region and a reduction of IQ by an average of about nine points (P = 0.022), after adjusting for the potential confounding factors.


CONCLUSIONS
Exposure to high iodine concentrations in drinking water has detrimental effects on the intelligence of children.
Liu
Hong-Liang
HL
Tianjin Centers for Disease Control and Prevention, 76 Hualong Road, HeDong District, Tiahjin 300011, People's Republic of China. hongliang.liu@sina.com
Lam
Lawrence T
LT
Zeng
Qiang
Q
Han
Shu-qing
SQ
Fu
Gang
G
Hou
Chang-chun
CC
D002648:Child; D002681:China; D005260:Female; D006306:Health Surveys; D006801:Humans; D007360:Intelligence / Q000187:drug effects*; D007455:Iodine / Q000009:adverse effects / Q000032:analysis*; D008297:Male; D012111:Residence Characteristics; D014881:Water Supply / Q000032:analysis*
D007455:Iodine